The stomach cramps. The frequent trips to the bathroom. Diarrhea is a common side effect in people receiving treatment for cancer. Diarrhea may also be caused by the cancer itself. But diarrhea can be more than an inconvenience for people with cancer — it can be a sign of something much more serious.

What causes diarrhea in people with cancer?

Everyone gets diarrhea now and then. If you have cancer, the common causes of diarrhea can still affect you. But there are additional causes of diarrhea specific to cancer, including cancer treatment, infections, stress and anxiety, and cancer itself.

Cancer treatment
Several types of cancer treatment can cause diarrhea:

Chemotherapy. In addition to killing cancer cells, chemotherapy tends to kill other fast-growing cells, such as those in your intestinal lining. If your chemotherapy causes sufficient damage to the lining of your intestine, diarrhea may result. Not all chemotherapy drugs cause diarrhea. Ask your doctor about your specific type of treatment.

Radiation therapy. Radiation therapy that focuses on your abdomen or pelvis, or that is given to your whole body, can cause diarrhea. How severe your diarrhea will be depends on your radiation dose. But the diarrhea can persist for weeks or months after treatment.

Surgery. If your surgeon must remove certain parts of your intestine in order to remove your cancer, this might alter your intestines' ability to absorb nutrients or fat and may result in diarrhea.

Bone marrow stem cell transplant. Chemotherapy and total body radiation therapy given as part of a bone marrow stem cell transplant can cause diarrhea. Diarrhea can also be a complication of graft-versus-host disease if you received bone marrow stem cells from a donor. In graft-versus-host disease, the transplanted bone marrow stem cells reject your body.

Infections
Cancer treatment can make you more susceptible to various infections, which can cause diarrhea. In addition, the antibiotics that may be used to treat an infection can cause diarrhea.

Stress and anxiety
The stress and anxiety that you feel when you're fighting cancer also can cause diarrhea.

The duration and severity of your diarrhea depend on what's causing your signs and symptoms. Talk to your doctor about what you can expect and how long your diarrhea may last.

When should you call your doctor?

Diarrhea typically causes stomach cramps and loose, watery stools. Mostly it's an inconvenience. But if your symptoms persist or get worse, it could be a sign of something more serious. Diarrhea can also lead to other problems, such as severe dehydration.

Some signs and symptoms are more serious than others are. Call your doctor right away if you have any of the following:

Six or more loose bowel movements a day for more than two days

Blood in your stool

Inability to urinate for 12 hours or more

Inability to drink liquids

Weight loss due to diarrhea

Diarrhea after several days of constipation

Severe abdominal pain

Fever of 101 F (38.3 C) or higher

Shaking chills

If your diarrhea doesn't seem severe but starts to interfere with your daily activities, such as if you're concerned about leaving home or going somewhere without a bathroom nearby, talk to your doctor. If abdominal cramping is keeping you from your daily activities, discuss this with your doctor, as well.

Also call your doctor if you're taking chemotherapy in pill form and you experience diarrhea. Your doctor can determine whether it's safe for you to continue taking chemotherapy pills.

Legal Conditions and Terms

Reprint Permissions

A single copy of these materials may be reprinted for noncommercial personal use only. "Mayo," "Mayo Clinic," "MayoClinic.org," "Mayo Clinic Healthy Living," and the triple-shield Mayo Clinic logo are trademarks of Mayo Foundation for Medical Education and Research.